One and Only
by JustBeFree
Summary: AU Erin and Jay story. Erin goes to work one morning to find a figure from her past sitting at her fathers desk. With old hurts being opened back up and other that never seemed to close. How will everything work out?
1. Surprise

_**This is my first time writing a PD fic. The title of this fic is from Adele ~ One and Only. This is AU but will eventually have some of the shows storylines introduced.**_

Erin walked into the precinct waving at Platt before making her way to intelligence. Walking up the steps she noticed there was something off. Platt hadn't been her usual way towards her and right now the office was to quiet. Although her father had called her in earlier than usual so no one had gotten in yet.

"Dad" Erin swung his office door open seeing someone else sitting there. "Oh I'm sorry" Erin went to walk back out the door.

"Kid stop" Voight stood up from his desk walking around the table to sit on it. "Erin meet your new partner, Jay Halstead"

"Is this supposed to be a joke because it isn't funny?" Erin raged as the man himself turned around to look at her. Her heart started beating uncontrollably; it had been what a little under two years. "This isn't happening"

"Kid, Halstead is good police. " Police? Wait the last she heard he was in the rangers. What was her father's game? "He'll have your back better than anyone."

"Is this about me getting shot?" Erin shuck her head. Her father was always protective but had been overly since she got shot two months back by some dealer.

"No this is about you having good back up someone we can trust." Trust now that was something her and Jay hadn't had in a long time. Now she knew why Platt was so weird this morning.

"Erin, I want to join the unit if you don't want me too" "Don't turn this around on me Halstead" Erin practically growled. "You want in fine" Erin through her hands up in the air.

"You won't regret this Hank." Jay turned to the older man.

"I better not. The only reason you're hired is because you're good police. I don't want you hurting my girl again. We clear on that Halstead?" Voight towered over him. He wasn't about to watch history repeat itself.

"I was stupid. I'm not going to leave that happen again." Jay said standing up from the chair watching as Erin got the new case ready.

"You better not Jay or else I won't be so forgiving"

X X X

"So are we going to talk at all?" Jay asked as Erin turned the radio up louder. She really wanted to pretend this wasn't happening. Jay turned the radio back down. "We're partners we kind of got to communicate."

"And what would you like to talk about?" Erin could think of a few things she wanted to talk about. She needed to keep her head in the game.

"I'm sorry about everything Er." Jay sighed as they pulled up to take some witness statements. "If I could change things you know I would." Like the time before that Erin thought.

"We got a case this isn't the time to talk about our personal lives." Erin said as she got out of the car walking towards the witnesses. After getting the statements the headed back to the station in silence.

"Erin" Erin walked towards Platt while Halstead kept walking to intelligence. She loved work but she guessed she was going to hate it now. "You doing ok, with him here?"

"Best I can" Erin said truthfully to the woman she thought of as an aunt.

"You're a strong girl. Don't let it get to you." Platt said as Erin already started walking to intelligence. She was about to give a debriefing to the rest of the unit. She need her head right.

"Erin "Antonio first greeted her as she stood off the last step and into intelligence. "What the hell is going on?"

"You would have to ask my old man that one Dawson. He sprung it on me this morning. I didn't even know he was back in town." Erin looked to where Halstead worked on his desk. It was good having him back around but things ended so badly between them.

"I wouldn't like to be Voight right now. I got you" Antonio fist pumped her as Alvin watched his goddaughter from a distance.

"So you've got a new partner" Jules quizzed as Erin got some coffee. "He's hot. I don't know how an office romance would go down with your pops."

"Nothing is going to happen with me and Jay." Erin was sure of that. She wasn't going back there like EVER.

"Uh huh." Jules smirked walking out of the break room. This was going to be a long ass day.

X X X

They had caught the bad guys and everyone was happy to be going home. "Linds" Erin stopped what she was doing to look at Jay. "Can we go somewhere to talk? We can't work like this."

Erin knew he was right they were going to be partners and there was a lot of stuff that needed to be said. "Call to the house after, I'll be there we can talk then." She didn't give him time to answer just walked out the door. Jay shoved his locker closed before exiting the same door.

Jay pulled up to the familiar house. It was weird seeing in from this perspective, he was a guest now. Walking up the familiar steps he knocked a few times before Erin answered. She looked beautiful and more relaxed than she was at work. "Come in" Jay followed her down the familiar hall and into the kitchen. "I thought you might be hungry." Erin had made their favorite risotto a lot of people didn't know Erin Voight was an amazing cook. She turned her back taking two beers out of the fridge handing him one and opening the other for her.

"You wanted to talk Halstead" Erin said as she pushed her now empty plate away. The silence when they had eaten wasn't awkward but it wasn't perfect.

"I wanted to say I'm sorry. The way I left…It wasn't right. You had stuck by me through everything and I couldn't for you, for us." Jay put down his beer. "I just hope that one day we can get back to what we were."

"I…I don't know Jay. It's been two years, you left me by myself. I was so lost; my dad didn't know what to do. Jason he was on a downward spiral, you know he's in jail right?" No, Jay didn't know that, a wave of guilt hit him. Jason was like a little brother to him too always hanging around him and Erin.

"I'm sorry Er…I should have been there for our family." Jay squeezed her hand. Erin let him do it for a second before pulling away.

"Your right you should have been. " Erin ran her fingers through her hair. "Where have you been the last two years?"

"I…I went to New York. Will is working their after coming back from overseas. I did my police exams there. I just couldn't face Chicago. _I couldn't face you_ , he left unsaid. When I got myself together, Will saw how miserable I was. He knew I needed you, I was too stubborn. Then he reminded me of when I was seven years old."

" _You know we're going to get married one day." A seven year old Jay Halstead told Erin Voight the biggest tomboy he knew. They had lived across the street from each other all their lives._

" _Nah uh boys are stupid" Erin stood from the sandbox arms folded walking away from the love struck Jay. Jay father was one of the surgeons at Chicago Med while Erin's father was a detective. Both their mothers were stay at home moms as their father's jobs took up so much time._

" _Jay, Jay where's Erin?" Jay turned to look at his ten year old brother Will. Will had always tried to mind Erin and Jay. Looking over he saw Erin climbing a tree while Camille and his mom Anna were fussing over a two year old Justin._

" _I was told that I had to watch you two. Come on let's get Erin." Will instructed as Jay stood up with a huff._

" _Erin come on we got to go get some ice-cream." Will told the younger girl as she swung out of the tree._

" _Ok Will" Erin said in a sing song voice dropping from the tree. "I'll race you both there" Before they could answer Erin was already racing ahead of them._

"You told me we'd get married, I guess you knew what we both wanted." Erin sighed thinking back to the many memories they had together.

" _Marry me?" Jay Halstead was bent on one knee in the sandbox he once told her he would marry her in. Erin looked at the ring wiping away the lone tear falling down her cheek. The ring he had in his hands was Anna's, his mothers. It was always Erin's favorite. "I don't want to let anything else come between us, not my father moving me half way across Chicago, me joining the rangers or you becoming a cop. You and me, Er this is it."_

" _Yes Jay." Jay picked her up swinging her around kissing her with everything he had. "Erin Halstead" Erin put her hand up admiring her ring._

" _I like the sound of that" Jay said as they walked towards his jeep. It wasn't anything over the top but it was special to them. Erin and Jay didn't do romantic but they loved each other like nothing else. They were married a week later in a small ceremony in their local church. It was quick and they didn't care. Jay was off to the rangers a couple days later._

"I don't know how to fix this" Jay admitted. Right now Erin didn't know if he could. He had walked away from her at the most difficult times of her life. Both their lives, they had been through everything together.

" _Sick she can't be sick" Erin said with a shaky lip as she looked at her father. She was fifteen Justin was ten their mother couldn't have cancer._

" _It's aggressive Erin. Your Mom doesn't have a lot of time left." Voight stopped to stop his voice from cracking. This was a talk he never thought he would have to her with his kids. They had caught the cancer too late and now it was spreading with no luck of stopping. Cami had wanted everything to be normal for the family as long as possible. Voight had agreed because who was he to go against his dying wife's wishes._

" _But why Mom?" The floodgates had opened and the tears were flowing steadily down Erin's face. "She can leave us, she can't" Voight pulled his daughter into a tight hug._

" _I know Er it's not fair but it's happening we just got to be strong for your Ma and Justin." Voight said as his little girl sobbed into his chest. Erin should have know something was wrong. Her mother hadn't been ok for a while. "I'm going to get Justin into bed we can tell him tomorrow he's so excited for his game let's not ruin it for him." Telling a fifteen year old was one thing but his ten year old was completely different. Erin nodded running her hands over her face before she even knew what she was doing she was outside Halsteads door opening it and running into Jay's bedroom. They had been going out for over two years now._

" _Er what's wrong?" Jay hugged his girlfriend tight._

" _My mom Jay, my mom she's dying." His heart broke for his girlfriend and for the Voight's. He had grown up with them. Cami was his mother's best friend. His own tears started rolling down his cheeks. "I'll be here for you babe, through everything,"_

 _Cami died just after Erin's sixteenth birthday. It had hit them all hard especially Hank. Erin learned how to drive and they got his mom to look after Justin when Erin or Hank weren't around. Everything was finally getting back to as normal things could when Jay's mother got sick. Will was off saving the world and wouldn't come home to help his mother. A brain tumor, she lasted a little under a year._

 _Everything was so up in the air Jay's father decided to move house to be closer to the hospital and to keep Jay close. He didn't understand taking him from the Voights, the only family he had left was the worst decision. Erin and he had been together nearly five years. Things started to strain when he had to move schools. Erin was always laid back didn't get in to the whole popular thing but people just seemed to flock to her._

" _You're moving schools too" Erin ran a hand over her face Jay was already going to live a little over thirty minutes away. She could get over that, they could drive to see each other, they both had cars._

" _It's not by choice Er. You know my father." Erin knew once he decided something there was no changing his mind no matter how hard anyone tried._

" _Everything is going to be so different you know. You've always been there." Erin sighed running her hand over his naked torso. They were laying in Jays bed in his home. The one thing about both their fathers' long hours was it involved less sneaking around. Justin was gone to a sleepover at his friends._

" _Nothing is going to change between us. We got this Erin it doesn't matter if it's a car journey away or an ocean away, me and you that's it." Erin looked into Jays eyes, she believed him. They could make anything work, they had lost both their mothers and helped each other through that._

"I don't know if we can Jay. We lost our baby, you blocked me out, moved to New York and didn't contact until I saw you in my dad's office today. The rangers I dealt with, your PTSD I was there every step but I didn't just lose our baby, I lost you too."

X X X

 _ **So what do you guys think? Should I continue?**_


	2. Long Way To Happy

_**Thank you all for your support x**_

X X X

After their talk he left their house to the tiny apartment he was renting downtown. It was a far cry from his dream home with Erin. They had moved a block over from where they had grown up. He knew Erin didn't want to be too far from Voight or Justin. He on the other hand wanted to be far away from Mark and Will well he didn't know when he was going to comeback. It also gave him comfort to know while he was away Voight was just around the corner. It was a four bedroom home which was perfect for them, they always said two kids, three at a push. The extra room would be the study. It has a big sitting room, a huge kitchen and the backyard was massive. It was everything they had ever wanted. Erin had looked for weeks until he got back. They got it for an amazing. Jay phone buzzed picking it up from his night stand he saw Voight's name flash.

"Halstead" Jay sat up in his bed letting the covers fall ever so slightly. His attention was caught by the only picture in his room. The picture was of Erin and him on his motorcycle. His father was always throwing money at him to buy his love. It was his way of making up for never being home.

"Meet me at O' Hara's. I got an UC job for you." Voight didn't give Jay most choice. Whose boss calls at eleven o' clock at night? Getting up and getting dressed Jay sighed.

"I know I said you would be with Intelligence but the gang unit are looking for someone to infiltrate a gang. They're some scumbags taking money off local businesses. I need you to get in with Arthur." Voight slid his file across the table. "Try get in as a henchmen. Get to know his business build up some charges and Intel. You're new to Chicago. Arthur here has a few of our own on his payroll, no one is that lucky. No one will suspect you for a cop. Are you good with this? I can find someone else."

"No I can do this Hank." Jay looked at the man who was still technically his father-in – law. Was this Voight's way of keeping him from Erin? Or did he really think he was right for the job?

"Good to hear. You're going to be running this by Danny Shields. You need anything call me or Antonio." Finishing off his whiskey Voight stood from the table. "Jin will set up your undercover profile. It'll be done by the morning. Goodnight Jay, stay safe."

"You too" Halstead stuffed the file into his coat finishing off his beer and leaving through the same door Voight just did.

X X X

Jay turned up on time to the rest of intelligence sitting around filling in paperwork. He noticed however Erin's desk was empty. Was she that upset she wasn't coming to work.

"Hey Sarg I picked up the docs from Jin." Voight dropped the file he was reading. Halstead didn't need to be telling him this. "I just thought I would see Erin."

"Erin isn't working today." Voight picked back up the file in his hands. "Oh" Jay didn't know why he expected to get anything out of Voight. "She's gone to see Justin" Voights divulged as Jay was about to walk away.

"I'm sorry about that. I wish I was there when it happened." Jay rolled on his feet like he used to when he was a kid. "For all of you. I hope everything goes well for him when he gets out."

"Yeah, me too kid." Jay knew that was his queue to leave Voight.

X X X

Walking through the now familiar prison doors, Erin spotted her brother. It had been a while since his face was bruised. The first few weeks for him in here had been tough. "Hey bro" Erin smiled brightly at her brother.

"Hey sis" Erin got a genuine smile off her baby brother. It still pained her that they couldn't keep him out of here, like they had failed her mother. "You look good. How's your shoulder?"

Erin's shooting had been the topic of her brother and father's lips since it happened. "You care" Erin teased naturally. "I'm fine Justin nothing can keep a Voight down. I'm more worried about you."

"No need to worry I made a few friends. I think dad had something to do with it." Erin knew what their father had done. Erin had known he had gone to that Italian family for protection for him.

"When are you going to let him see you?" Justin had refused to see Voight. He blames him for being locked up in here. Didn't get that her father was locked up for a while too and she was left all alone.

"I don't want to talk about dad. I want to hear about you." The last time she had pushed he got the guards to bring him back to his cell.

"Jay is back." Erin sat back a little looking at the confusion on her brother's face. She knew her brother held the most resentment for Jay.

"What the hell is he doing back here?" Justin growled his fists clenching. He wanted nothing but to pound his fists into Halsteads face.

"He's my new partner." Erin ran a hand over her face. She still didn't know how she felt about everything, how Jay fit back into her life. She was just getting back to dating. "I don't know how to handle this. I don't know what to do Just. Everything is coming back and I just feel like I can't breathe."

"Hey you're going to be fine Er. You get that jackass that we call dad to get him out of the unit." Justin really wanted to see his father now maybe he could do an extra twenty in here. He'd be seen as a hero killing Hank Voight.

"I'll be fine, he just showed up in the unit yesterday. I need time to adjust Just. Don't worry about me ok? You just keep your head down it's only another few months. You're over half way there. I love you."

"I love you too Erin." Erin watched as her brother got taken back to his cell. She had to stop herself from crying. Her life was not what she expected.

X X X

"So how did you and Justin go?" Hank asked as him and Erin ate at their favourite restaurant. It had been where they all came for any occasion through the years. She remembers when her and Jay had their first major breakup this is where Voight had taken her.

" _What's up Erin?" Erin spun around on the chair in her father precinct as she waited for him to finish up an interrogation._

" _Nothing Dawson just having boy troubles." Erin rolled her eyes waiting for the newest rookie to give her shit._

" _Pretty girl like you shouldn't be having boy troubles." Antonio teased as Platt slapped the back of his head._

" _Going to give Auntie Trudy a hug?" Erin got from her seat giving Trudy Platt a hug. Platt was Antonio's training officer. She was also feared by most the police force._

" _It's been a while Trudy. You haven't been over for dinner." Erin quizzed the older woman. "It's a guy isn't it? "Platt rolled her eye at the younger girl. She knew full well her career meant more to her than any man. She was just about to take her detectives exam for a second time._

" _Erin everything alright kid?" Voight said approaching is nearly eighteen year old daughter. She did show up every now and again at the precinct but usually all her time went to Jay. "You and the boy fighting again?" Hank was a detective his daughter being miserable wasn't going to get passed him. Ever since this Allie kid came on the scene it had been messing with his girls head. She had overheard her on the phone a couple times telling Annie how Allie had a thing for Jay._

 _Tears sprang to Erin's eyes. "We broke up Dad." Erin wiped the tears from her face. Hank hadn't seen her cry since Anna Halsteads funeral. "Allie got to us. I told Jay she was into him but he wouldn't listen."_

" _Come on, O will handle here lets go to that Italian you love." Hank escorted his daughter who was supposed to be in school out of the precinct. In his mind he was thinking just how to make the kid pay. Also about how wrong Camille and Anna had been._

 _Erins phone buzzed for the hundredth time since they sat down every time Jays name flashed the screen. "You could turn that off kid?"_

" _It could be Justin. I've got to pick him up later." Erin wasn't going to get into it with her father about her brother ditching. She was still angry at Jay that he hadn't listened to her. It had happened over a week ago and it was getting too much so she eventually broke down to her father._

" _Halstead is a stupid kid Erin. He doesn't know how good he had it." Hank squeezed his daughter's hand. Her phone rang again and the both groaned. "It's Justin" "I got to go get him traffic is going to be a nightmare, thank you dad for this." Kissing his cheek she picked up her keys and purse._

" _No problem kid. You want me to sort the kid out you just tell me" Erin chuckled at her father giving him a final wave._

"He's Justin still bitter he got locked up" Erin took a spoon of her dish. The food was still the same as she remembered from being a little girl. "I told him Jay was back." Voight dropped his fork on the table. "Dad it's better he finds out now instead of walking into the precinct and seeing Jay there. He would be locked straight back up."

Voight took in what his daughter was saying. Although Erin had some of his temper Cami's good nature could be seen in her. Justin was his mini me, angry at the world. "You're right kid. I'm sorry I dumped that on you too. With his skills for the intelligence unit, his file was passed to me. If it doesn't work out in a few weeks, I'll get him moved. He's doing an undercover job at the minute so you got a couple weeks to find your feet."

"I will be ok, I just need time" Erin said truthfully to her father. She didn't need to start lying to him about her feelings. Voight's phone buzzed and he immediately picked it up.

"It's a CI. I got to go but we're still good for dinner on Sunday." Erin put down her drink as her father through money on the table which would more than cover the bill. "Always." She hadn't missed one yet since her mother died.

X X X

"Jay" Erin said as she stepped on to the porch her hand on her holster ready to pull her weapon out. What the hell was he doing here? She didn't need this right now. It had been a long draining day. She hated seeing Justin locked up.

"I wanted to come see if you were alright. I had to stop by the precinct. Your dad told me where you were today." He just turns up after all this time and thinks everything can go back to normal. Does he really think she will spill her heart out to him?

"You should go Jay." Erin sat down beside him on the porch bench. She had loved this man when he was just a boy. She still loved him but he had broken her in a way no one else did. "This…this shouldn't be happening. Our marriage ended when you walked out that door. You can't come back here after two years and push things, it doesn't work like that."

"I fucked up Er." Jay said looking at the floor. She didn't even know he was crying until his body started shaking. She hadn't seen him cry since the day they got told they had lost their baby. "I need us back. I need everything to make sense again."

"Shh" Erin wrapped her arms around him like it was second nature. "I need time Jay. You hurt me so bad, worse than you have ever done before." Erin thought their biggest relationship issue was Allie.

 _Everything had been going fine for a couple of months until this girl Allie started circling Jay. Jay had said they were just friends and Erin believed him because she knew Jay. The fact she didn't know Allie was beginning to frustrate her. "Why is she calling again?" Erin sipped her soda as she sat across from her distracted boyfriend._

" _Math, she's really bad at it. You got my entire attention babe." Jay kissed his girl over the table. Erin had killer instincts, she blames the long line of cops she comes from. Something wasn't right about how Allie was all about her guy._

" _Looking for you to tutor her?" Erin moved some food around her plate. She hated being insecure. She wasn't the jealous type everyone knew Jay was off limits but a new school he was fresh meat._

" _Erin you got to stop this. She lives across the street from me." Jay had been nice to Allie because being his neighbour; she was the first person he had met from his new school. Their friendship had grown over the last few months but he would never betray Erin._

 _Erin raised a brow at Jay as she threw some notes on the table which pissed Jay off. He always paid. His father threw cash at him to fill up the void of him working every hour. "Sound familiar Halstead?"_

" _Erin you got to stop this. You don't trust me?" Jay hadn't thought of the whole neighbour scenario but Erin should trust him._

" _I feel like we're going in circles. I don't trust her Jay." Erin flipped her aviators onto her face as the exited the diner already beginning to find her keys. She knew right now if she stayed her temper would get the better of her._

" _You don't know her." Jay deadpans. His rayban sunglasses cover his ice blue eyes. They never had a fiery relationship until they fought and he could count those times on one hand. "You want to meet her? Would that make this better? I don't want to fight Er." Jay pulled her to him._

" _A little. I don't know Jay just something ain't sitting right with me about this." Erin was never one to bite her tongue she wouldn't lie to Jay. "Come to my house. Your dad is off right? He's got Justin all day." Erin nodded because he did, unfortunately._

 _Pulling up into the Halsted drive in her old mustang, Jay's new jeep shined in the rare sunlight. Erin was always a sucker for a classic. "Jay, hey." Erin held in her grown as she heard the female voice approach them. "Oh you must be Erin" Erin knew that smile, saw it plenty of times. She was the obstacle that needed to be moved out of the way. "It's nice to finally meet you." She extended her hand as Jays arm went around Erin's waist._

" _Allie right?" Allie nodded. "Jays told me a lot about you. Nice to finally put a face to the name." Erin accepted her hand shake as Jay kissed her head. "You live across the street right?"_

" _Uh huh just like you and Jay before right?" Erin nodded with the fakest smile on her face. Sitting outside on Jay's new porch she watched as the kids played around._

" _That blonde kid right there is Allies little brother Ben. He's a good kid reminds me of having Justin around." Erin sipped her coffee. What was this parallel universe? Back on their street it was Erin and Justin. Here it was Allie and Ben. She bit her tongue for once she wasn't going to argue in front of Allie._

" _So Allie you got a guy?" It was a simple question she wasn't going to sound like a dick asking. Jay sat looking a college brochure._

" _I did but we broke up a few months back. We just didn't click anymore you know? So how long have you and Jay been together?_

" _Coming up to five years." Allies smile faltered slightly. Boys were so stupid. Jay probably played it down that they weren't together so long. "We've know each other forever. Halstead here just grew on me" Jay chuckled lightly pulling her into his lap kissing her when she got comfortable._

" _This one took so much convincing. I ask her to marry me when we were seven and she told me no boys are stupid. I've been hooked ever since." Jay remembered one of his oldest memories._

" _Wow that is majorly adorable." Allie saddened as she watches them share the same look of amusement._

" _Me and Linds here we don't think we've been called adorable before." Jay chuckled. He was amazed that Hank Voight ever let him near his little girl. He thinks it was more Camille's charm on Voight he has to thank._

" _Linds?" "My middle name is Lindsay some people call my Linds mostly the Halsteads and their meathead friends." Erin remembers when they found out her middle name. Thought it would work for them to tease her._

" _Wow you guys really do have lots of history. I have cheerleading practice so I'll leave you guys to it. It was nice meeting you Erin. Jay I will see you tomorrow." Allie started to walk away._

" _Nice to meet you too." Erin said politely. Erin looked from the corner of her eye to see a boy around their age watching Ben Corsen. "What's the deal with that guy?" Erin threw over her shoulder to Jay._

" _I don't know. He seems real quiet, I think his name is Lonnie. Why are you checking him out?" Jay laughed as he kissed her neck._

" _Nah I just got a vibe something isn't right with him." Erin said as she kissed Jay. The guy was just standing there watching the kid._

" _You are so your dad's daughter." Jay teased as he lifted her over his shoulder and brought her into the house._

 _X X X_

 _ **Happy Halloween. It'll be a few days before another update….I have other fics to update.**_


End file.
